In one aspect, this invention relates to a method for the transportation and placement of water-in-oil emulsion explosive compositions. In a further aspect, this invention relates to an apparatus for the transportation and placement of emulsion explosive compositions including means for providing a substantially annular stream of a lubricating fluid surrounding the stream of emulsion explosive passing through a conduit.
The use of explosive emulsion compositions in various types of blasting operations has dramatically increased in recent years because of the economy and excellent explosive characteristics of such compositions. Basically, emulsion explosives comprise a water-in-oil emulsion wherein the oil phase is a hydrocarbon fuel component and the dispersed aqueous phase is an aqueous solution of inorganic oxidizing salts. Various other materials, including sensitizing agents and additional fuels for example, can be employed in a variety of different formulations. Typical water-in-oil emulsion explosive compositions are set forth in detail in U.S. Pat. No. 3,447,978 to Bluhm.
As is the case with other types of water containing slurry explosive compositions, one preferred method for placing the explosive composition into a detonation site, such as a borehole for example, includes pumping the emulsion explosive from a storage container thereof through a conduit and into the detonation site. While the pumping characteristics of any given explosive emulsion will vary with its composition and physical properties, the external oil phase of the emulsion causes these types of explosive compositions to be relatively difficult to pump through conduits. For example, emulsion explosive may exhibit pressure drops of from about 4 to about 7 psi per foot of one inch I.D. hose when pumped at a rate of 50 lbs./min. Thus, for example, to deliver an emulsion explosive from a storage supply thereof through a fifty foot length of such conduit, the discharge pressure at the pump employed with the system would be required to be in the range of from about 200 to about 350 psi. Thus, until recently, on site transportation and placement of emulsion explosives from storage tanks to detonation sites required heavy duty pumping apparatus capable of generating large pressure heads. Furthermore, pumping of such explosive emulsions through long lengths of conduit is practically prohibited. Also, the use of check valves in the pumping system under such high pressure presents a detonation hazard.
Another important consideration with respect to pumping explosive emulsion is that such compositions must be handled in a manner which ensures that the emulsion will not "break". That is, the explosive emulsion must not be subjected to such high shear stresses that the emulsion structure degrades (such as in the case when pumped at high pressures). It is important that the emulsion explosive not be allowed to intermix with other fluids to an extent which can adversely affect the explosive properties thereof once it has been placed into a detonation site, such as a borehole, for example.